Controllable pitch propeller



Jan. 18, 1938. c. PRESTQN Elf/M 2,105,843

CONTROLLABLE FITCH PROPELLER FiledlNov. 29, 1935 Patented Jan. 18, 1938CONTROLLABLE FITCH PROPELLER Charles I. Preston and *HarryA MelvilleWilliamspo rt, Pa., assignors to AviationManuy "facturing Corporation,Chicago; IlL, a. corporation of Delaware Application November zo, 1935,serial No. y,52,151 s calma (ci. 17o-163)" The invention relates tohydraulic mechanism for controllable pitch propellers.

In aircraft, it is now'common practice tovuse lubricating-oil from theinternal combustion engine which drives the propeller to operatehydraulic means for changing the pitch of the propeller-blades.Heretofore, it has been customary to freely pump lubricating-oil fromthe engine to the hydraulic means. This frequently,

in the event of a substantial leak or breakage in the pitch-changemechanism, resulted in reducing the pressure and volume of oil in thelubrication-system of the engine and, in some instances, below thatrequired for proper lubrication suilieiently to cause engine failure ordamage.

The object of the invention is to provide improved. hydraulic mechanismfor controllable pitch propeller-blades, in which oil from the engine,which drives the propeller, is used for operating said mechanism, and inwhich provision is made for limiting the volume of lubricating-oil whichcan be taken from the engine for the operation of the pitch-Varyingmechanism.

By providing in the line for the oil from the engine to the hydraulicmechanism a limited rate of flow the engine, notwithstanding anybreakage of, or substantial loss in, oil in the hydraulic mechanism,will not interfere with the lubrication of the engine. The maximum rateof iiow of the oil to said mechanism is limited so that lubricating-oilpressure in the'engine will never be reduced to such an extent as tointerfere with the efficient lubrication of the engine or to causefailure from lack of lubrication. The maximum rate of iiow may be so lowthat the amount of oil normally added to the engine will compensate forthat used in the hydraulic mechanismk even if loss of the oil should bepermitted by the 40 latter.

This object isattained primarily by providing between the pressure oilline and the hydraulic mechanism for adjusting thepitch of thepropeller-blades, a restricting device or nozzle whichlimits the rate offlow of the oil to said mechanlsm, so that the drop in volume at themaximum flow will not interfere with the proper lubrication of theengine and also by providing, be-

tween the flow-restricting device and the hydraulic pressure mechanism,an accumulating chamber of limited capacityso that the pump forsupplying the lubricant `to the fluid pressure mechanism may deliversuiiicient oil to operate said mechanism but no more than theaccumulated volume in said chamber resulting from the flow-restrictingdevice. Other objects of the invention will appear from the detaileddescription. l

The vinvention consistsin the several novel 5 features hereinafter setforth and more 'particularly defined by claims at the conclusionthereof.

In the drawing:

Fig. 1 is a central longitudinal section'through a portion of theinternal combusion engine and l0 an aircraft propeller to whichtheinventionis applied. Fig. 2 is anenlarged section illustrating thedevice for restricting the rate offlowof lubricating oil from'` theengine to ther accumulating .chamber from which oil is delivered to 15the hydraulic mechanism. Fig. 3 is a view of the devices connecting thefluid pressure operated piston and the propeller-blades for pitchadjustment. g

The invention is exemplified in a structure 20 comprising an internalcombustion engine a, a propeller shaft bfdriven fromv the crank-shaft cof the engine through suitable reduction gearing d, a housing d5 whichencloses the reductiongearing and isadapted to retain lubricating-oil,25'

a propeller hub e, in which propeller-blades f are rotatably mounted forpitch variation and hydraulic mechanism for shifting the bladesfor pitchvariation which comprises a fluid-cylinder g fixedly mounted on thefront end of the hub e, 30 a piston h in said cylinder, movable in onedirection by the lfluid underpressure, links i pivotally connected tothe piston and connected, respectively, to arms k on the Shanks` of thepropellerblades, and springs r for retracting thepiston h 35' whenpermitted by the reduction of fluidA pressure in the cylinder g. Thereduction gearing d comprises a gear` d1 which is connected to rotatewith the crank-shaft c, aninternally toothed ring-gear d2 fixed to thepropeller shaft b.and,40 intermediate pinions fd? whichlare journaledin. a head d4 mounted,` between the engine-casing and the housing d5 forthe reduction-gearing. The housing d5 carries at its front end a bearingb1 for the propeller shaft. The engine is 45 equipped with the usualpump (not shown) and lines for circulating lubricating oil underpressure from a suitable Weller oil-sump, usually iny the bottom of thecrank-.case a, to all the parts of the engine and auxiliary equipmentwhich 50l require lubrication, afs, well understood in the art. Themechanism thus far described may be of any Vsuitable type' orconstruction known in' theart.

Oil from the' engine is used for operating the" 55 plstonh. to vary thepitch oi' the propeller blades f. For this purpose the piston hisprovided with a hollow stem h', which is slidable in the shaft b andprovided with a packing-ring hz at its inner end to form a fluid-tightilt between the bore of the propeller shaft and the hollow stem of thepiston. A head I2 is xed in the shaft b, inwardly of the piston-stemIl', and an oil-V delivery pipe I3 having its ends ilxed in head I 2 andshaft b, is adapted to deliver oil from an annular channel in a ring I5,which is fixed to rotate with the propeller shaft b, and is providedwith piston-rings I8 to prevent escape of oil through the bearing b' forthe shaft. Oil forced to the oil-ring I5 passes through pipe I3,thepropeller-shaft b in front of the` head I2. and the hollow stem h'oi' the piston h.to react on the outer end of the piston and operate theylinks i for rotating the propeller-blades f onk their own axes toincrease the pitch of the blades. In this type of propeller, theincrease of oil pressure in the cylinder 'a operates the blade-shiftingmechanism to reduce the pitch and. Don decrease oi' pressure, thecounter force serves to increase the pitch of the blades. Thisexemplliles hydraulic mechanism operable by oil under pressure forshifting the propeller-blades to vary their pitch.

The lubricant lines comprise a pipe II for delivering oil under pressurefrom theoil-pump for the engineinto a passage l in the head d', fromwhich it llows to a forwardly leading duct Vl' in the housing d5 to anow-restricting device for limiting the -rate of ilowfrom the pump tothe hydraulic pitch-controlling mechanism. This device consists of anozzle 12,'which is screwed into the housing d5 and has a 'smail'orrestricted oriiice l3 which limits the'rate of ow of oil from the engineto any accumulating chamber l, into which this nozzle discharges theoil. This chamber is formed by a partition-wall l in and in#- tegralwith the housing d5 and is adapted to con-- tain a limitedquantity ofoil, such for'example as a quart, or approximately a sumcient for'theoperation of the hydraulic'mechanism.

. This partition separates the chamber l* from the y: chamber in thehousing which contains the lubricant for the reducing gearing. yOverilow and vent pipes l7 are provided lto permit `the excess oil whichmay accumulate inchamberl l* to flow back into the housing d5 fromwhichit willow back into the oil well in the motor.

'An important attribute of nozzle l2r and the chamber l* for retaining alimited'supply of oil for use in the hydraulic mechanism, is .thatthe'maximum rate of flow of oil the dow-restricting from the oil-pumpfor the engine is reduced. to Y such an extent that the flow of oil tothe cham ber 14 for use in the hydraulic mechanismpswill beinsumcie'ntat all times to interfere witl'the dnormal pressure of oilrequired for lubrication of the engine'and the auxiliary parts. Thechamber I4 permits a limited quantity of oil to accumulate from theflow-restricting nozzle for the operation of the'hydraulio mechanism.The ratev of ilow into chamber I4 is far below the capacity of pump m..As a result. the pump cannot, at any time, draw oil from the engine at agreater rate of flow than that permittedby the nozzle l Should thechamber l4 be drained by the pump, no additional oil can'be'deliveredtoy the cylinder U, by pump m except the small quantityperml'tted toenter said chamber through nozzle l. The maximum rateof ilow throughVthis nozzle is so low thatin the event of theloss of the oil from the'hydraulic` mechanism, onaccount of breakquantity n the bottom-wall ofchamber 14, so that it can be readily removed for cleaning purposes.This plug is locked in place by a split-ring 1G.

A pump m is provided for forcing oil under pressure to the cylinder gfor operating piston h. `This pump is driven by a verticalshaft m' whichis ournaled in a sleeve 1n2 which extends vertically throughV thechamber I4. A ge'ar mi, which is integral with ring I5, is secured torotate with the 4propeller-shaft and drives a bevelled gear ma xed tothe upper end of shaft m 4to drive the pumpm. A duct n leads fromoil-chamber I4 to the intake of the pump. A duct n' leads from thedischarge side of the pump to ring I5. From ring I5, the oil is forcedthrough pipe I3, propeller-shaft b and piston-stem h' to the cylinder g.y

A speed-controlled governor s, preferably of the ily-ball type, as wellunderstood in the art, is driven by the pump-shaft m to operate apressure regulating valve t, which permits some of the oil from therhydraulic cylinder a to ilow into the oil compartment I4. A cable t' isusually connected to the governor, so that the regulating valve t mayalso be manually controlled.

During the operation of the propeller-shaft, the oil-pump of the enginewill force oil through pipe I0, duct l', and nozzle l2 into theoilcompartment 14. The pump m'will be driven from the propeller-shaft ata speed proportionate to the propeller and engine Ispeed and draw oilfrom the contents of chamber l* through intake duct n and force itthrough the discharge duct n', ring I5, pipe il and piston-stem h',yinto the outer end of they cylinder a. 'Ihe pressure of the voil will begoverned by the valve t under control oi' the speed-controlled governors. and the manual control cable t' to control the pressure inthecylinder a and the corresponding pitch-changes effected by the movementof the piston h in said cylinder. l

The oil delivered* to chamber I4, from which the pump m takes itssupply. enters said chamber through ducts l. l1 and nozzle l, whichislprovided with the restricted oriilce l, to limit the rate of ilowiromtheoil sump or well a" of the engine to the chamber 1. p `of oil takenfrom the oil-well or sump of the As a result, the volume conditions, thepressure of oil in the engine will' be quickly reduced, which results inengine failure or injury due to inadequate lubricant.

With the present invention, the vmaximum rate of ow of oil through thenozzle l2 to the' chamber -l4 for use in the hydraulic pitch-changemechanism, is so low that it is impossible to bleed the 'oil supply inthe engine. As a'result, it becomes impossible to kdeplete the supplyofoil in the lubricating system of the engine by the hydraulicpitch-change mechanism.

The invention exemplifies hydraulic pitchchange mechanism for\propellers in which oil under pressure for operating said mechanism isderived from the supply of lubricating-oil for the engine and in whichthe rate of flow of the oil from the engine is restricted to preventreduction of pressure of lubricating-oil in the engine or from reducingit sufficiently to cause insuicient or ineflicient lubrication of theengine and its associated parts.

The invention is not to be understood as restricted to the details setforth, since these may be modified within the scope of the appendedclaims, without departing from the spirit and scope of the invention.

Having thus described the invention, what we claim as new and desire tosecure by Letters Patent is:

1. 'I'he combination with a variable pitch propeller provided withhydraulic means for varying the pitch of the propeller blades, ofmeansfor delivering lubricating oil under pressure from theengine-lubricating system, comprising a constantly open device forrestraining the rate of flow of oil from the engine suiiiciently toprevent substantial reduction of the oil pressure in the lubricatingsystem to less than that required for proper lubrication of the engine,means for accumulating a sufiicient quantity of oil from thenow-restricting device to operate the pitch-change means, and means fordelivering oil from the accumulating means to theV hydraulicpitch-changing means.

2. The combination with a variable pitch propeller provided withhydraulic means for varying the pitch of the propeller blades, of meansfor delivering lubricating oil under pressure from theengine-lubricating system, comprising a constantly open nozzle with anorice for restricting the rate of ow of oil from the engine sufcientlyto prevent substantial reduction of the oil pressure in the lubricatingsystem to less than that required for proper lubrication of the engine,means for accumulating a suicient quani tity of oil from theflow-restricting device to operate the pitch-change device, andcontrollable means for delivering oil from the accumulating means to thehydraulic pitch-changing means.

3. The combination with a variable pitch propeller provided withhydraulic vmeans for varying the pitch ofthe propeller blades, of meansfor delivering lubricating oil under pressure from theengine-lubricating system, comprising a constantly open device forrestricting the rate of flow of oil from the engine sui'ilclently toprevent substantial reduction of the oil pressure in the lubricatingsystem to less than that required for proper lubrication of the engine,means fo'r accumulating a suiiicient quantity of oil from theflow-restricting device lto operate the pitch` the pitch of thepropeller blades, of means for'de-` livering lubricating oil underpressure from the engine-lubricating system, comprising a removable plughaving a constantly open .orice for restricting the rate of iiow of oilfrom the engine sufiiciently to prevent substantial reduction of the oilpressure in the lubricating system to less than that required for properlubrication of thev ing the pitch of the propeller blades, of ahousingthrough which the shaft of the propeller exi' tends, a chamber inthe housing for accumulating a sulcient quantity of oil to operate thepitch-changing meansmeans for delivering oil under pressure from theengine-lubricating system Jto the chamber, comprising a constantly opendevice for restricting the rate yof ilow of oil from the enginesuiilciently to prevent substantial reduction of the oil pressure in thelubricating system to less than that required for` .proper lubricationof the engine, and controllable means for delivering oil from theaccumulating chamber to the hydraulic pitch-'changing means.

6. The combination with a variable pitch propeller, provided withhydraulic means for varying the pitch of,V the propeller blades, of ahousing through which the shaft of the propeller extends,

Aa chamber in the housing for accumulating a suihcient quantity.of oilto operate the pitchchange means, means for delivering oil underpressure from the engine-lubricating system to the chamber, comprising aplug in, and removable from the outside of, the housing, having aconstantly open orice for restricting the rate oi tlow or oil from theengine sufiiciently to prevent substantial redction of the oil pressurein the lubricating system to less than that required for properlubrication ot the engine, and controllable means for delivering oilfrom the accumulating chamber to the hydraulic pitchchanging means.

'7. The combination with a variable pitch propeller, provided withhydraulic means for varying the pitch of the propeller blades, of ahousing through which the shaft of the propeller extends, a chamber inthe housing for accumulating a suiiicient quantity of oil to operate thepitchchange means, means for delivering oil under pressure from theengine-lubricating system to the chamber, comprising a duct in thehousing and a removable -plug inthe housing, having a constantly openorice for restricting the rate o! flow of oil from the enginesufficiently to prevent substantial reduction of the oil pressure in thelubricating system to less than `that required for proper lubrication ofthe engine, and controllable means for delivering oil from theaccumulating chamber to the hydraulic pitchchanging means.

8. 'I'he combination with a variable pitch propeller, provided withhydraulic means for varying the pitch of the propeller blades, ofv ahousing through which the shaft of the propeller extends, a chamber inthe housing for accumulating ya sufficient quantity of oil to operatethepitch-change means, means for delivering oil under pressure from theengine-lubricating system, comprising ar constantly open device forrestricting the rate of ilow of oil from the engine sufficiently toprevent .i substantial reduction of the oil pressure in the lubricatingsystem to less than that required for proper lubrication of-the engine,a pump driven from the propeller shaft `and connected to the housing fordelivering oil from the accumulating chamber to the hydraulicpitch-changing means.

CHARLES I. PRESTON. H. MELVILLE HAMMILL.

